Monorail sortation system

ABSTRACT

A universal cross belt sorter system ( 1 ) consisting of four major components: a monorail track ( 26 ), a drive car ( 20 ), multiple cross belt cars ( 24 ) and system controls. The drive cars ( 20 ) pull multiple cross belt cars ( 24 ) along the track ( 26 ). The cross belt cars ( 24 ) are typically loaded with material, which is then discharged into outlets. An outlet may be a chute, a bin, a conveyor, a truck, etc. Sortation systems are typically used to consolidate material according to selected pa-rameters, such as zip code, customer order, to replenish a specific store and many other identifying information. The cross belt cars ( 24 ) are loaded with material at induction areas ( 3 ). The types or methods of inducting material onto the cross belt cars ( 24 ) range from manual to semi-automatic to fully automatic.

This application claims priority from U.S. provisional application Ser.No. 60/418,795, the disclosure of which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

This invention relates generally to sortation systems and moreparticularly to monorail sortation systems.

Automated material handling and sortation systems are known forreceiving, transporting and discharging goods among various stations inlarge scale sortation operations, for example warehousing, distribution,postal sortation and handling of mail and packages, and airport baggagehandling, to name a few. Whatever the operation, goods typicallyoriginate from one location within the facility and must be sorted andtransported to several different locations for further handling, ororiginate from several locations within a facility and must betransported to a single location such as a shipping dock. The manner inwhich the goods are sorted and selectively distributed among variousstations in a facility of course depends on the nature of the operation.

One known sortation and delivery method involves using powered belt orroller conveyers to transport individual items or sorted loads of itemsto various destinations within a facility. When goods from multiplesources must be delivered to a single station, associated take awayconveyors must be merged onto a main conveyor or discharge point. Thisrequires careful coordination of each item as it arrives to prevent jamsor damage. Each merge point on such a conveyor system would accordinglyrequire a complex system of sensors, start/stop controls, actuators,power supply lines, etc. Similarly, when items must be delivered tomultiple destinations or stations in a facility, a main conveyor must beprovided with diverter apparatus to direct individual items or batchesof items to either continue or be diverted at various points. Eachdiverter apparatus would require an additional closed system includingsensors, actuators, control mechanisms, wiring and power supply toaccomplish the diverting operation and track and identify the itemsbeing diverted.

The disadvantages of conveyor-type systems have led to the developmentof tracked systems. In one known type of system, a closed loop trackcarries cars propelled by a continuous belt or chain drive. The cars areequipped with open trays which can be loaded from chutes, andsubsequently tilted to unload their carloads into bins which are locatedaround the track. These cars are often termed “dumb” because they do notinitiate any sorting actions, but rather respond to stimuli from theinduction stations to discharge their load. For example, car speed iscontrolled by a track-side motor which circulates the belt or traindrive, and car dumping is controlled by track-side dumping mechanisms.Such systems are designed for long term installations which sort andtransport large volumes of goods. Although these closed loop tracksystems are an improvement over conveyor-type systems, the complexity oftheir track, drive and tilting mechanisms makes it a major undertakingto set them up or rearrange their sortation layout. They must be shutdown for nearly all maintenance tasks.

The foregoing illustrates limitations known to exist in presentsortation systems. Thus, it is apparent that it would be advantageous toprovide an alternative directed to overcoming one or more of thelimitations set forth above. Accordingly, a suitable alternative isprovided including features more fully disclosed hereinafter.

SUMMARY OF THE INVENTION

In one aspect of the present invention, this is accomplished byproviding a sortation system comprising: a longitudinally extendingmonorail track; a plurality of interconnected cars, at least one carbeing a drive car, and at least one car being an article conveying car.

In a second aspect of the present invention, this is accomplished byproviding a sortation system comprising: a longitudinally extendingmonolithic monorail track comprising: an upper wheel engaging section; alower wheel engaging section; and a power section, the upper sectionbeing connected to an upper portion of the power section and the lowersection being connected to a lower portion of the power section; amulti-conductor power bus mounted within the power section; twolongitudinally extending mounting flanges, each mounting flange having aU-shape, one side of the mounting flange U-shape being coincident with aportion of one side of one of the upper wheel engaging section and thelower wheel engaging section; and one side of the mounting flangeU-shape being coincident with a portion of one side of the powersection, wherein the upper wheel engaging section and the lower wheelengaging section are spaced apart, the track having a closed side beingclosed by the power section and an open side opposite the power section,the open side being between the upper wheel engaging section and thelower wheel engaging section; a plurality of interconnected cars, atleast one car being a drive car, and at least one car being an articleconveying car, the at least one drive car and the at least one articleconveying car each have a brush assembly slidably engaging the powerbus.

In a third aspect of the present invention, this is accomplished byproviding a sortation system comprising: a longitudinally extendingmonorail track; a plurality of interconnected cars, at least one carbeing a drive car, and at least one car being an article conveying car,each car includes two wheel assemblies, each wheel assembly engaging thetrack, each wheel assembly comprising: a plurality of spaced apart sidewheels, the side wheels rotating about a vertical axis; and an endwheel, the end wheel rotating about a horizontal axis, the end wheelbeing a caster, the caster swiveling about a vertical axis.

In a fourth aspect of the present invention, this is accomplished byproviding a track comprising: a longitudinally extending monolithicmonorail track having an upper wheel engaging section; a lower wheelengaging section; and a power section, the upper section being connectedto an upper portion of the power section and the lower section beingconnected to a lower portion of the power section; a multi-conductorpower bus mounted within the power section, wherein the upper wheelengaging section, the lower wheel engaging section and the power sectioneach have a U-shape, wherein the upper wheel engaging section U-shapehas its open side facing downward, the lower wheel engaging sectionU-shape has its open side facing upward, and the power section U-shapehas its open side facing horizontally; and the upper wheel engagingsection U-shape open side, the lower wheel engaging section U-shape openside and the power section U-shape open side all facing towards a commoncenter; and a plurality of interconnected cars, at least one car being adrive car, and at least one car being an article conveying car.

In a fifth aspect of the present invention, this is accomplished byproviding a drive car adapted for drivingly engaging a track comprising:a frame; a plurality of wheel assemblies attached to the frame; and amotor and drive wheel assembly attached to the frame, the motor anddrive wheel assembly being vertically movable relative to the frame, thedrive wheel being adapted to drivingly engage the track.

In a sixth aspect of the present invention, this is accomplished byproviding a drive car adapted for drivingly engaging a track comprising:a frame; a two wheel assemblies attached to the frame, each wheelassembly comprising: a plurality of spaced apart side wheels, the sidewheels rotating about a vertical axis; and an end caster wheel, the endcaster wheel rotating about a horizontal axis, the drive car having aforward direction of travel, one wheel assembly having the end wheel atan upper end of the wheel assembly and being forward of the other wheelassembly, the end wheel of the other wheel assembly being at a lower endof the wheel assembly; and a motor and drive wheel assembly attached tothe frame, the motor and drive wheel assembly being vertically movablerelative to the frame, the drive wheel being adapted to drivingly engagethe track, the motor and drive wheel assembly comprising: a cantileverbar attached to a rear part of the motor and drive wheel assembly, aportion of the cantilever bar distal from the motor and drive assemblybeing attached to the frame; and a slide assembly mounted between therear part of the motor and drive wheel assembly and the frame, the slideassembly comprising a slide slidably fitting within a slotted member,the slide assembly permitting the motor and drive wheel assembly to movevertically relative to the frame, the drive wheel being positionedbetween the wheel assemblies.

In a seventh aspect of the present invention, this is accomplished byproviding an article conveying car adapted for movably engaging a trackcomprising: a frame; an endless movable belt; at least three rotatablerollers attached to the frame, the movable belt being positioned aboutthe rollers; and at least one of the rollers being translatably moveablerelative to the movable belt.

In an eighth aspect of the present invention, this is accomplished byproviding a n article conveying car comprising: a frame comprising twoside plates connected by a plurality of cross bars; three rollersrotatably attached to the frame, the three rollers being arranged in atriangle; an endless movable belt about the rollers; two wheelassemblies attached to the frame, each wheel assembly comprising: aplurality of spaced apart side wheels, the side wheels rotating about avertical axis; and an end wheel caster at a lower end of the wheelassembly, a wheel of the end wheel caster rotating about a horizontalaxis; a bi-direction position controllable belt drive attached to theframe and operably connected to one of the rollers; and aninterconnection adapted to connect one article conveying car to one of adrive car and another article conveying car, the interconnectionincluding a mechanical connection and an electrical connection.

In a ninth aspect of the present invention, this is accomplished byproviding an article conveying car comprising: each article conveyingcar comprising: a frame comprising two side plates connected by aplurality of cross bars, and a reduced friction plate having a groovetherein; three rollers rotatably attached to the frame, the threerollers being arranged in a triangle, each roller having a groovetherein; an endless movable belt about the rollers, the belt having arib extending therefrom, the belt rib tracking in at least one of thereduced friction plate groove and the roller grooves; two wheelassemblies attached to the frame; and a bi-direction positioncontrollable belt drive attached to the frame and operably connected toone of the rollers.

The foregoing and other aspects will become apparent from the followingdetailed description of the invention when considered in conjunctionwith the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a plan view of a monorail sortation system according to thepresent invention;

FIG. 2 is an end view of a monorail track for use with the sortationsystem shown in FIG. 1;

FIG. 3 is a perspective view of the monorail track shown in FIG. 2,illustrating the power bus;

FIG. 4 is a second perspective view of the monorail track shown in FIG.2, illustrating the mounting flanges;

FIG. 5 is an end view of a section of the monorail track shown in FIG.2, illustrating the engagement of a wheel assembly with the track;

FIG. 6 is a perspective view of the tow car shown in FIG. 1;

FIG. 7 is a perspective view of the tow car shown in FIG. 6, without acover;

FIG. 8 is a side view of the tow car shown in FIG. 6;

FIG. 9 is a side view of the lower portion of the tow car shown in FIG.6;

FIG. 10 is a perspective view showing the details of the motor and drivewheel assembly;

FIG. 11 is a perspective view of the cross belt car shown in FIG. 1;

FIG. 12 is a perspective view of the cross belt car shown in FIG. 11,with the cross belt removed;

FIG. 13 is second perspective view of the cross belt car shown in FIG.11, with certain components removed; and

FIG. 14 is an end view of the cross belt car shown in FIG. 11.

DETAILED DESCRIPTION

FIG. 1 shows a sortation system 1 according to the present invention. Inthis sortation system 1, a continuous loop monorail track 26 supports acontinuous train of interconnected tow or drive cars 20, and cross beltor article conveying cars 24. In one embodiment, a drive car 20 can pullabout 24 article conveying cars. Although the drawings show a cross belttype car 24, other types of article conveying cars, such as a tiltingcar, can be used with the present invention. In addition to providingsupport for the cars 20, 24, the monorail track 26 also provideselectrical power through a power bus 36 attached to the track 26 to thecars 20, 24. In the preferred embodiment, DC power at 80 volts for thedrive motors and 24 volts for electronics is supplied through power bus36. Preferably, a wireless communication system is used to providecontrol signals from a central control system to the cars 20, 24.Alternatively, a wired communication system could be included in thepower bus 36.

Sortation system 1 includes multiple induction stations 3 where packagesor articles are loaded onto article conveying cars 24. Multiple bins 5accept the packages from the article conveying cars 24. When a packageis loaded onto to an article conveying car 24, the control system isupdated with information about the package, such as its destination, andassociates that package with that particular article conveying car 24.As the article conveying car 24 approaches the appropriate bin 5 forthat package, the control system signals the article conveying car 24 tounload the package into the appropriate bin 5. Alternatively, thecontrol system informs the article conveying car 24 of the location ofthe appropriate bin. The article conveying car 24 keeps track of itslocation relative to the appropriate bin 5 and unloads the package intothe appropriate bin.

Although there are many ways for the sortation system 1 to track thearticle conveying cars 24 relative to the appropriate bin 5, one methodused for the present sortation system uses photo sensors (not shown) onthe article conveying cars 24. When a package is loaded onto an articleconveying car 24, the control system tells the car 24 to unload thepackage XX flags from the loading station 3. Placed about the system 1are flags that are sensed by the photo sensors. For example, a packagegoing to Minneapolis is loaded onto car 24. The bin 5 for Minneapolispackages is positioned 27 flags from the loading station 3. The articleconveying car photo sensor senses the car 24 passing the flags. As thecar 24 approaches the 27th flag, a controller on the article conveyingcar 24 operates an unloading mechanism or belt 100 to unload the packageinto the Minneapolis bin. ID tags, preferably bar codes, 54 are providedon each car 20,24. A bar code sensor is used by the control system todetermine which car 24 is being loaded with what package so that theappropriate destination commands can be sent to the right articleconveying car 24.

FIGS. 2 through 5 show the features of monorail track 26 and theengagement of cars 20, 24 with track 26. Preferably track 26 is formedfrom multiple sections of either straight or curved monolithic extrudedtrack. Track 26 is preferably an aluminum alloy. Track 26 includes anupper section 30 attached to a power section 34 that has a lower section32 attached to it. Above and below the power section 34 are twolongitudinally extending mounting flanges 38. A power bus 36, such aspower conductors supplied by Vahle Electrification Inc. is mounted inpower section 34. Each car 20, 24 includes a removable brush assembly 52that slidably engages the power bus 36 so that power can be transferredto the cars 20, 24.

Mounting flanges 38 have two purposes. First, the flanges 38 are used toattach the track 26 to building structures, such as floors, walls orceilings. Mounting brackets 44 are used to secure track 26 to whateveradditional framework is needed to attach the track 26 to the appropriatestructure. The second purpose of mounting flanges 38 is to secure onesection of track 26 to an adjacent section of track 26 (See FIG. 3).Where two sections of track 26 are joined, jointers 42 are placed in themounting flanges 38 of the two sections of track 26. The jointers 42extend between the two sections of track 26 and are secured withfasteners or other mounting hardware.

Both types of cars 20, 24 use similar wheel assemblies 80 to attach thecars 20, 24 to the track 26. Each wheel assembly 80 consists of a centermember 82 that is removably attached to a wheel assembly support 50.Wheel assembly support 50 is then attached to car 20, 24. Rotatable sidewheels 84 are attached to the ends of center member 82. Side wheels 84roll against the sides of track upper and lower sections 30, 32. Endwheel(s) 88 are attached to either end, or both ends, of center member82. Preferably, end wheel 88 uses a caster mount 86 that allows endwheel 88 to swivel as car 20, 24 moves through a section of curvedtrack. Preferably, each car 20, 24 uses two wheel assemblies 80. In oneembodiment, both end wheels 88 on an article conveying car 24 are at thelower end of the wheel assemblies 80. In another embodiment of a drivecar 20 (see FIG. 9), one end wheel 88 is at the lower end of one wheelassembly 80 and one end wheel 88 is at the upper end of the other wheelassembly 80. The forward wheel assembly (relative to the direction oftravel as shown by arrow 90) has the end wheel 88 at the upper end ofwheel assembly 80. The forward wheel assembly 80 can optionally have asecond end wheel 88 at its lower end, as shown in FIG. 9.

FIGS. 6 through 10 shows the details of drive car 20. Drive car 20includes a frame formed from two side plates 60 and two cross bars 58.The article conveying car 24 uses a similar frame. A motor and drivewheel assembly 62 is attached to the rear of drive car 20. The motor anddrive wheel assembly consists of a DC servo or positionable controllablemotor 92 connected to a friction drive wheel 64 through a reducer andright angle drive 94. Drive wheel 64 engages the upper surface of track26. Motor and drive wheel assembly 62 is suspended from the rear of car20 by a cantilever arm 96 and a slide assembly 98. Cantilever arm 96 isattached to the reducer and right angle drive 94. The free end ofcantilever arm 96 is attached to the frame of car 20. Slide assembly 98consists of a slide on the reducer and right angle drive 94 that fitswithin, and slides within, a corresponding slotted block attached to theframe of car 20. This attachment arrangement for the motor and drivewheel assembly 62 suspends all the weight of the motor and drive wheelassembly 62 from the rear of car 20, allows the motor and drive wheelassembly 62 to move vertically, and thereby increases the downward forceon drive wheel 64. Having all the weight at the rear of car 20 causescar 20 to tip up slightly in the front, see FIG. 8. Therefore, theforward wheel assembly 80 has the end wheel 88 at the upper end of thewheel assembly so that the end wheel 88 can ride against the inside topsurface of the upper section of track 26.

Drive car 20 includes a wireless control signal receiver or modem 66 forreceiving control signals from the central control system. The modem 66can also be used for sending status information and error messagesregarding the sortation systems cars back to the central control system.Modem 66 is connected to a computer 68 that in turn is connected to a DCservo controller 70. Depending upon the modem 66 and the DC servocontroller 70 being used, modem 66 could be directly connected to the DCservo controller 70 thereby eliminating the computer 68. Car 20 includesa DC/AC inverter 72 that takes power from the power bus 36 via brushassembly 52 to supply AC power to any electronic components requiring ACpower. A power supply 74 is provided to provide appropriate power tocomputer 68.

In operation, the central control system uses RF signals to broadcastcontrol signals to drive cars 20 and to article conveying cars 24.Wireless modem 66 receives the control signals for both drive cars 20and article conveying cars 24 and passes them to the computer 68, whichthen passes the control signals to the DC servo controller 70. DC servocontroller 70 has two functions. First, it uses the control signals tosend the appropriate control signals to DC servo motor 92 to move car20. Second, it passes the control signals for the article conveying cars24 through interconnection 56 to the other cars. Drive car 20 andarticle conveying car 24 use a CAN® bus network for inter-carcommunication. Interconnection 56 includes both a physical connection(see FIG. 8) and an electrical connection (see FIG. 7). Depending uponthe characteristics of the controller 70 and the computer 68, thelocation where these functions are performed could change.

For a continuous sortation system, as shown in FIG. 1, the control ofthe multiple drive cars 20 has to be coordinated to evenly drive thecontinuous system. In one embodiment, the central control system sendscommands to a lead drive car and the lead drive car coordinates theoperation of the other drive cars. Alternatively, the central controlsystem can coordinate the operation of all the drive cars and sendindividual commands to each drive car.

FIGS. 11 through 14 show the details of the article conveying car 24.Car 24 includes a frame formed from side plates 60 connected by twocross bars 58, similar to the frame for a drive car 20. Rotatablerollers 102, 106 are mounted on the cross bars 58. One roller 102 is adrive roller. The other roller 106 is preferably nondriven. A thirdroller 104 is positioned below rollers 102, 106 such that the threerollers form a triangle. Roller 104 is vertically movable and can beadjusted by threaded adjuster 110. A belt 100 is placed about the threerollers 102, 104, 106. Roller 104 is then adjusted to achieve thedesired tension on belt 100. Belt 100 is preferably formed from a UHMW(Ultra High Molecular Weight) polymer, preferably a reduced frictionpolymer. A reduced friction UHMW polymer plate 120 is placed below theupper horizontal extent of belt 100. Plate 120 provides support for belt100 when a package has been placed on car 24. Belt 100 includes a rib122 extending below the belt. Rib 122 is essentially co-extensive withthe length of belt 100. Corresponding grooves 118 are formed in thethree rollers, 102, 104, 106 and plate 120. Tracking of the belt 100 ismaintained by rib 122 tracking in grooves 118. This eliminates the needfor side plates 60 to extend above belt 100 to maintain proper trackingof belt 100. It also eliminates the need for any roller adjustmentmechanisms to adjust the tracking of belt 100. Without raised sidesextending above belt 100, a large or long package can span two articleconveying cars 24.

Car 24 includes a bi-directional DC servo motor 112 that is connected todrive roller 102 by drive belt 114. Preferably, both DC servo motor 112and drive roller 102 include drive sprockets 116 and drive belt 114 is agrooved or ribbed timing belt. In one embodiment, roller drive sprocket116 is cut into the end of roller 102. Car 24 includes a DC servocontroller similar to the DC servo controller 70 for drive car 20. TheDC servo controller receives commands from the central control systemthrough interconnection 56 via a drive car 20 and any article conveyingcars 24 between the DC servo controller and the drive car 20. In oneembodiment, a car 24 includes a photo sensor (not shown) that countsflags (not shown) to determine the position of car 24. When thedesignated number of flags have been counted, the DC servo controlleroperates DC servo motor 112 to move belt 100 causing a package to bemoved from car 24 into a bin 5. When a large or long package has beenplaced on two adjacent article conveying cars 24, the DC servocontroller for the lead or forward car operates its belt 100 firstcausing the package to turn towards bin 5. Next belt 100 on thefollowing car is operated ejecting the turned package into bin 5. Wherebin 5 is large enough to accept a long package without it being turnedfirst, belts 100 on both cars 24 are operated together to eject the longpackage into bin 5.

An intercar plate 124 is attached to the leading edge of car 24. Plate124 extends across the gap between adjacent cars 24 and under the belt100 on the leading car 24 (See FIG. 12). Plate 124 generally has arectangular shape. In the preferred embodiment, plate 124 is formed ofLexan® polycarbonate resin.

In an alternate embodiment of sortation system 1, the drive cars 20 andarticle conveying cars 24 are combined into combination drive andarticle conveying cars. Preferably, this is accomplished by using alinear induction motor.

Linear electric motors belong to a special group of electrical machinesthat convert electrical energy directly to mechanical energy intranslational motion. While all electric motors operate based onprinciples of electromagnetic interactions, there are different types ofmotors. Polyphase synchronous motors and induction motors both usealternating current as input electricity source. Direct current motorsare normally used for small horsepower applications. Conceptually, anyrotary motor has a linear counterpart. There are linear synchronousmotors (with permanent magnet or wound field), linear induction motors,and linear direct current motors.

A linear electric motor is perhaps best understood by imagining thestator of an ordinary electrical motor being cut, unrolled and stretchedlengthwise. An appropriate conductive material like copper, aluminum, orother material is positioned next to the unrolled stator. Thealternating current in the unrolled stator provided by conventionaltechniques magnetically interacts with the conductive material to createa moving field of magnetic force acting on both the stator and theconductive material. The vehicle may be slowed down or stopped byreversing the polarity of that moving field.

A linear induction motor (LIM) consists of a primary and a secondary.When powered by three-phase alternating current, a moving flux isproduced in the primary winding. Current induced in the secondary reactswith the flux, producing a mechanical force. Both the primary and thesecondary of LIMs are flat structures. The interaction of flux andcurrent moves the secondary linearly. A linear synchronous motor (LSM)has a similar structure, except that its secondary must be either apermanent magnet or a wound field with a direct current. The word“synchronous” comes from the fact that the primary magnetic field andthe secondary magnetic field in a LSM move at the same speed.

A mount 108 is provided in side plates 60 to mount a reaction plate(aluminum and mild steel plates sandwiched together) bolts to each car24. Linear motors bolt to the track parallel to the reaction plate witha small air gap. An AC drive powers the linear motor coils to propel thearticle conveying cars 24.

1. A sortation system comprising: a longitudinally extending monolithicmonorail track, the monorail track comprising: a U-shaped upper wheelengaging section; a U-shaped lower wheel engaging section; a U-shapedpower section, the upper wheel engaging section being connected to anupper portion of the power section and the lower wheel engaging sectionbeing connected to a lower portion of the power section; and twolongitudinally extending mounting flanges, each mounting flange having aU-shape, one side of the mounting flange being coincident with a portionof one side of one of the upper wheel engaging section and the lowerwheel engaging section; and one side of the mounting flange beingcoincident with a portion of one side of the power section, the upperwheel engaging section having its open side facing downward, the lowerwheel engaging section having its open side facing upward, and the powersection having its open side facing horizontally; and the upper wheelengaging section open side, the lower wheel engaging section open sideand the power section open side all facing towards a common center; anda plurality of interconnected cars, at least one car being a drive car,and at least one car being an article conveying car, each carcomprising: an interconnection connecting one car to an adjacent car,the interconnection including a mechanical connection and an electricalconnection; and a plurality of wheel assemblies, each wheel assemblyengaging the track, each wheel assembly comprising: a plurality ofspaced apart side wheels, the side wheels rotating about a verticalaxis, one side wheel engaging the upper wheel engaging section, theother side wheel engaging the lower wheel engaging section; and an endwheel, the end wheel rotating about a horizontal axis, the end wheelengaging one of the upper wheel engaging section and the lower wheelengaging section, the end wheel including a caster swiveling about avertical axis; each drive car comprising: a drive car frame; two wheelassemblies attached to the drive car frame; a motor and drive wheelassembly attached to the drive car frame, the motor and drive wheelassembly being vertically movable relative to the drive car frame, adrive wheel of the motor and drive wheel assembly engaging the track,the drive wheel being positioned between the wheel assemblies, the motorand drive wheel assembly comprising: a cantilever bar attached to a rearpart of the motor and drive wheel assembly, a portion of the cantileverbar distal from the motor and drive wheel assembly being attached to thedrive car frame; and, a slide assembly mounted between the rear part ofthe motor and drive wheel assembly and the drive car frame, the slideassembly comprising a slide slidably fitting within a slotted member,the slide assembly permitting the motor and drive wheel assembly to movevertically relative to the drive car frame; a control signal receiver; acontrol signal transmission device adapted to transmit control signalsto another drive car and to an article conveying car; and a controller,the controller receiving control signals from the receiver, transmittingcontrol signals to the motor and drive assembly and transmitting controlsignals for at least one of another drive car and an article conveyingcar to the control signal transmission device, wherein the controlsignal receiver, the control signal transmission device and thecontroller including a CAN serial bus network and wherein theinterconnection electrical connection is electrically connected to thecontrol signal transmission device; each article conveying carcomprising: an article conveying car frame comprising two side platesconnected by a plurality of cross bars, and a reduced friction platehaving a groove therein; three rollers rotatably attached to the articleconveying car frame, the three rollers being arranged in a triangle,each roller having a groove thereabout, one of the rollers beingtranslatably movable; an endless movable belt about the rollers, thebelt having a rib extending therefrom, the belt rib tracking in at leastone of the reduced friction plate groove and the roller grooves; twowheel assemblies attached to the article conveying car frame; and abi-direction position controllable belt drive attached to the frame andoperably connected to one of the rollers.
 2. A sortation systemcomprising: a longitudinally extending monorail track; a plurality ofinterconnected cars, at least one car being a drive car, and at leastone car being an article conveying car.
 3. The sortation systemaccording to claim 2, wherein at least one car is a drive and articleconveying car.
 4. The sortation system according to claim 3, wherein thedrive and article conveying car includes a linear induction drive. 5.The sortation system according to claim 2, further comprising: aninterconnection connecting one car to an adjacent car, theinterconnection including a mechanical connection and an electricalconnection.
 6. The sortation system according to claim 2, wherein themonorail track comprises: an upper wheel engaging section; a lower wheelengaging section; and a power section, the upper wheel engaging sectionbeing connected to an upper portion of the power section and the lowerwheel engaging section being connected to a lower portion of the powersection.
 7. The sortation system according to claim 6, wherein each carincludes a plurality of wheel assemblies, each wheel assembly engagingthe track, each wheel assembly comprising: a plurality of spaced apartside wheels, the side wheels rotating about a vertical axis, one sidewheel engaging the upper wheel engaging section, the other wheelengaging the lower wheel engaging section; and at least one end wheel,the at least one end wheel rotating about a horizontal axis, the atleast one end wheel engaging one of the upper wheel engaging section andthe lower wheel engaging section.
 8. The sortation system according toclaim 7, wherein the at least one end wheel is at a lower end of thewheel assembly.
 9. The sortation system according to claim 7, whereinthe at least one end wheel is at an upper end of the wheel assembly. 10.The sortation system according to claim 9, wherein the car has a forwarddirection of travel, the forwardmost wheel assembly having the at leastone end wheel at the upper end of the wheel assembly.
 11. The sortationsystem according to claim 6, wherein the upper wheel engaging section,the lower wheel engaging section and the power section each have aU-shape.
 12. The sortation system according to claim 11, wherein theupper wheel engaging section has its open side facing downward, thelower wheel engaging section has its open side facing upward, and thepower section has its open side facing horizontally; and the upper wheelengaging section open side, the lower wheel engaging section open sideand the power section open side all facing towards a common center. 13.The sortation system according to claim 6, wherein the upper wheelengaging section and the lower wheel engaging section are spaced apart,the track having a closed side being closed by the power section and anopen side opposite the power section, the open side being between theupper wheel engaging section and the lower wheel engaging section. 14.The sortation system according to claim 6, further comprising: amulti-conductor power bus mounted within the power section.
 15. Thesortation system according to claim 14, wherein the at least one drivecar and the at least one article conveying car each have a brushassembly slidably engaging the power bus.
 16. The sortation systemaccording to claim 6, wherein the monorail track further comprises: atleast one longitudinally extending mounting flange.
 17. The sortationsystem according to claim 16, wherein the mounting flange has a U-shape,one side of the mounting flange being coincident with a portion of oneside of one of the upper wheel engaging section and the lower wheelengaging section; and one side of the mounting flange being coincidentwith a portion of one side of the power section.
 18. The sortationsystem according to claim 17, wherein there are two longitudinallyextending mounting flanges.
 19. The sortation system according to claim6, wherein the monorail track is monolithic.
 20. The sortation systemaccording to claim 2, wherein each car includes a plurality of wheelassemblies, each wheel assembly engaging the track, each wheel assemblycomprising: a plurality of spaced apart side wheels; and at least oneend wheel, the at least one end wheel rotating about a horizontal axis.21. A sortation system comprising: a longitudinally extending monolithicmonorail track comprising: an upper wheel engaging section; a lowerwheel engaging section; and a power section, the upper wheel engagingsection being connected to an upper portion of the power section and thelower wheel engaging section being connected to a lower portion of thepower section; a multi-conductor power bus mounted within the powersection; two longitudinally extending mounting flanges, each mountingflange having a U-shape, one side of each mounting flange beingcoincident with a portion of one side of one of the upper wheel engagingsection and the lower wheel engaging section; and another side of eachmounting flange being coincident with a portion of one side of the powersection, wherein the upper wheel engaging section and the lower wheelengaging section are spaced apart, the track has a closed side beingclosed by the power section and an open side opposite the power section,the open side being between the upper wheel engaging section and thelower wheel engaging section; a plurality of interconnected cars, atleast one car being a drive car, and at least one car being an articleconveying car, the at least one drive car and the at least one articleconveying car each have a brush assembly slidably engaging the powerbus.
 22. A sortation system comprising: a longitudinally extendingmonorail track; a plurality of interconnected cars, at least one carbeing a drive car, and at least one car being an article conveying car,each car including two wheel assemblies, each wheel assembly engagingthe track, each wheel assembly comprising: two vertically spaced apartside wheels, the side wheels rotating about a vertical axis; and an endwheel, the end wheel rotating about a horizontal axis, the end wheelbeing a caster, the caster swiveling about a vertical axis.
 23. Thesortation system according to claim 22, wherein the end wheel of onewheel assembly is at an upper end of the wheel assembly and the endwheel of the other wheel assembly is at a lower end of the wheelassembly.
 24. The sortation system according to claim 22, wherein theend wheel of each wheel assembly is at a lower end of the wheelassembly.
 25. A track comprising: a longitudinally extending monolithicmonorail track having: an upper wheel engaging section; a lower wheelengaging section; a power section, the upper wheel engaging sectionbeing connected to an upper portion of the power section and the lowerwheel engaging section being connected to a lower portion of the powersection; and a multi-conductor power bus mounted within the powersection, wherein the upper wheel engaging section, the lower wheelengaging section and the power section each have a U-shape, wherein theupper wheel engaging section has its open side facing downward, thelower wheel engaging section has its open side facing upward, and thepower section has its open side facing horizontally; and the upper wheelengaging section open side, the lower wheel engaging section open sideand the power section open side all facing towards a common center. 26.The track according to claim 25, further comprising: two mountingflanges, each mounting flange having a U-shape, one side of the mountingflange being coincident with a portion of one side of one of the upperwheel engaging section and the lower wheel engaging section; and oneside of the mounting flange being coincident with a portion of one sideof the power section.
 27. A drive car adapted for drivingly engaging atrack comprising: a frame; a plurality of wheel assemblies attached tothe frame; and a motor and drive wheel assembly attached to the frame,the motor and drive wheel assembly being vertically movable relative tothe frame, a drive wheel of the motor and drive wheel assembly beingadapted to drivingly engage the track.
 28. The drive car according toclaim 27, wherein there are two wheel assemblies and the drive wheel ispositioned between the wheel assemblies.
 29. The drive car according toclaim 27, wherein each wheel assembly comprises: a plurality of spacedapart side wheels, the side wheels rotating about a vertical axis; andan end wheel, the end wheel rotating about a horizontal axis.
 30. Thedrive car according to claim 29, wherein the end wheel comprises acaster swiveling about a vertical axis.
 31. The drive car according toclaim 29, wherein there are two wheel assemblies, the drive car having aforward direction of travel, one wheel assembly having the end wheel atan upper end of the wheel assembly and being forward of the other wheelassembly, the end wheel of the other wheel assembly being at a lower endof the wheel assembly.
 32. The drive car according to claim 27, whereina rear end of the motor and drive wheel assembly is attached to theframe.
 33. The drive car according to claim 32, further comprising acantilever bar attached to the rear end of the motor and drive wheelassembly, a portion of the cantilever bar distal from the motor anddrive wheel assembly being attached to the frame.
 34. The drive caraccording to claim 32, further comprising a slide assembly mountedbetween the rear end of the motor and drive wheel assembly and theframe, the slide assembly comprising a slide slidably fitting within aslotted member, the slide assembly permitting the motor and drive wheelassembly to move vertically relative to the frame.
 35. The drive caraccording to claim 27, wherein the motor and drive wheel assemblyincludes a right angle gear reducer between a motor of the motor anddrive wheel assembly and the drive wheel.
 36. The drive car according toclaim 27, wherein a motor of the motor and drive wheel assembly is aposition controllable drive motor.
 37. The drive car according to claim27, further comprising: a control signal receiver; and a control signaltransmission device adapted to transmit control signals to another drivecar and to an article conveying car.
 38. The drive car according toclaim 37, further comprising: a controller, the controller receivingcontrol signals from the receiver, transmitting control signals to themotor and drive wheel assembly and transmitting control signals for atleast one of another drive car and an article conveying car to thecontrol signal transmission device.
 39. The drive car according to claim38, wherein the control signal receiver, the control signal transmissiondevice and the controller include a CAN serial bus network.
 40. Thedrive car according to claim 38, further comprising: an interconnectionadapted to connect a drive car to one of another drive car and anarticle conveying car, the interconnection including a mechanicalconnection and an electrical connection.
 41. The drive car according toclaim 39, wherein the electrical connection is electrically connected tothe control signal transmission device.
 42. A drive car adapted fordrivingly engaging a track comprising: a frame; two wheel assembliesattached to the frame, each wheel assembly comprising: a plurality ofspaced apart side wheels, the side wheels rotating about a verticalaxis; and an end caster wheel, the end caster wheel rotating about ahorizontal axis, the drive car having a forward direction of travel, onewheel assembly having the end wheel at an upper end of the wheelassembly and being forward of the other wheel assembly, the end wheel ofthe other wheel assembly being at a lower end of the wheel assembly; anda motor and drive wheel assembly attached to the frame, the motor anddrive wheel assembly being vertically movable relative to the frame, adrive wheel of the motor and drive wheel assembly being adapted todrivingly engage the track, the motor and drive wheel assemblycomprising: a cantilever bar attached to a rear part of the motor anddrive wheel assembly, a portion of the cantilever bar distal from themotor and drive wheel assembly being attached to the frame; and a slideassembly mounted between the rear part of the motor and drive wheelassembly and the frame, the slide assembly comprising a slide slidablyfitting within a slotted member, the slide assembly permitting the motorand drive wheel assembly to move vertically relative to the frame, thedrive wheel being positioned between the wheel assemblies.
 43. The drivecar according to claim 42, further comprising: a control signalreceiver; and a control signal transmission device adapted to transmitcontrol signals to another drive car and to an article conveying car.44. An article conveying car adapted for movably engaging a trackcomprising: a frame; an endless movable belt; at least three rotatablerollers attached to the frame, the movable belt being positioned aboutthe rollers; and at least one of the rollers being translatably moveablerelative to the movable belt.
 45. The article conveying car according toclaim 44, further comprising an adjuster attached to each end of thetranslatably movable roller.
 46. The article conveying car according toclaim 45, wherein the adjuster includes a threaded apparatus attached tothe translatably movable roller.
 47. The article conveying car accordingto claim 44, wherein there are only three rotatable rollers, only one ofthe three rollers being translatably movable.
 48. The article conveyingcar according to claim 44, wherein the at least three rollers arearranged in a triangle.
 49. The article conveying car according to claim44, wherein the movable belt is bi-directionally movable.
 50. Thearticle conveying car according to claim 44, further comprising a lowfriction plate attached to the frame and positioned below a portion ofthe belt.
 51. The article conveying car according to claim 44, furthercomprising: a belt alignment system comprising a first alignment memberon the belt and a second alignment member on at least one of the frameand at least one roller, the first alignment member engaging the secondalignment member.
 52. The article conveying car according to claim 51,wherein the first alignment member comprises a rib on the underside ofthe belt and the second alignment member comprises a groove.
 53. Thearticle conveying car according to claim 52, wherein the secondalignment member comprises a groove in the at least three rollers. 54.The article conveying car according to claim 52, wherein the frameincludes a reduced friction plate below a portion of the belt and thesecond alignment member comprises a groove in the plate.
 55. The articleconveying car according to claim 44, further comprising: a plurality ofwheel assemblies attached to the frame, each wheel assembly adapted toengage the track, each wheel assembly comprising: a plurality of spacedapart side wheels, the side wheels rotating about a vertical axis; andat least one end wheel, the at least one end wheel rotating about ahorizontal axis.
 56. The article conveying car according to claim 55,wherein the at least end one wheel comprises a caster swiveling about avertical axis.
 57. The article conveying car according to claim 55,wherein the at least one end wheel is positioned at a lower end of thewheel assembly.
 58. The article conveying car according to claim 44,further comprising a position controllable drive attached to the frameand operably connected to the belt.
 59. The article conveying caraccording to claim 58, wherein the position controllable drive isbi-directional.
 60. The article conveying car according to claim 58,wherein at least one roller is a drive roller and has a sprocketthereon, and the position controllable drive includes a timing beltengaging the sprocket.
 61. The article conveying car according to claim60, wherein the sprocket is integrally formed with the drive roller. 62.The article conveying car according to claim 44, further comprising: aninterconnection adapted to connect one article conveying car to one of adrive car and another article conveying car, the interconnectionincluding a mechanical connection and an electrical connection.
 63. Thearticle conveying car according to claim 44, further comprising: a plateextending away from the frame, the plate adapted to slidably fit beneaththe belt on an adjacent article conveying car.
 64. The article conveyingcar according to claim 63, wherein the plate has a rectangular shape.65. An article conveying car comprising: a frame comprising two sideplates connected by a plurality of cross bars; three rollers rotatablyattached to the frame, the three rollers being arranged in a triangle;an endless movable belt about the rollers; two wheel assemblies attachedto the side plates, each wheel assembly comprising: a plurality ofspaced apart side wheels, the side wheels rotating about a verticalaxis; and an end wheel caster at a lower end of the wheel assembly, awheel of the end wheel caster rotating about a horizontal axis; abi-direction position controllable belt drive attached to the frame andoperably connected to one of the rollers; and an interconnection adaptedto connect one article conveying car to one of a drive car and anotherarticle conveying car, the interconnection including a mechanicalconnection and an electrical connection.
 66. The article conveying caraccording to claim 65, further comprising a car drive attached to theframe and adapted to drivingly engage a track.
 67. The article conveyingcar according to claim 66, wherein the car drive is a linear inductiondrive.
 68. An article conveying car comprising: a frame comprising twoside plates connected by a plurality of cross bars, and a reducedfriction plate having a groove therein; three rollers rotatably attachedto the side plates, the three rollers being arranged in a triangle, eachroller having a groove therein; an endless movable belt about therollers, the belt having a rib extending therefrom, the belt ribtracking in at least one of the reduced friction plate groove and theroller grooves; two wheel assemblies attached to the frame; and abi-direction position controllable belt drive attached to the frame andoperably connected to one of the rollers.